Hemopexin-like repeats - Hemopexin

Hemopexin is a serum glycoprotein that binds haem and transports it to the liver for breakdown and iron recovery, after which the free hemopexin returns to the circulation. Hemopexin prevents haem-mediated oxidative stress. Structurally hemopexin consists of two similar halves of approximately two hundred amino acid residues connected by a histidine-rich hinge region. Each half is itself formed by the repetition of a basic unit of some 35 to 45 residues. The hemopexin domain exhibits the shape of an oblate ellipsoidal disk. The polypeptide chain is organised in four beta-sheet (blades) I to IV, which are almost symmetrically arranged around a central axis in consecutive order, giving rise to the formation of a four-bladed propeller. Each propeller blade or repeat is made up of four antiparallel beta-strands connected in a W-like strand topology, and is strongly twisted.